Summary: | 碩士 === 台北醫學院 === 細胞及分子生物研究所 === 84 === Abstract Vaccinia virus (VV) is an enveloped
DNA virus with wide host range andenters cells via plasma
membrane fusion. Previous studies have identified amonoclonal
antibody(mAb) B2 that recognized cell surface molecules and
neutralized 95% VV infection by blocking virus binding. In
addition, lambda expression cloning with this mAb resulted in
isolation of a 4.2 kb cDNA cloneA1. This A1 cDNA contains an
open reading frame (ORF) of 1,300 amino acidsand shares no
homology with any known sequences in database. The major
objectives of this study are to analyze the gene product of A1
cDNA and to determine if it facilitated VV entry. A1 cDNA was
fused with bacteria glutathione-S-transferase (GST) to produce
A1-GST fusion protein,which intern was used as an antigen to
generate more monoclonal antibodies that could block VV
infection. Four mAbs 1-5E-5H mAb, 5-4H-3B mAb,4-6G-5B mAb, and
4-1D-5G mAb were isolated. 1-5E-5H and 5-4H-3B could
approximately contribute to 95% of efficiency for blocking the
virus infection,while 4-6G-5B and 4-1D-5G mAb could only reach
29% and 50% respecitvely. In order to map out the epitopes
within A1 protein for these mAbs, aseries of A1-GST 3'-deletion
clones were generated. The result indicated thatthese mAbs
recognize four different epitopes localized at the N-terminal
regionof A1. In addition, these mAbs also stain cell surface
indicating that the recognition sites were situated outside of
cells. Therefore, this A1 protein couldbe a type I transmenbrane
protein. To understand whether the A1 gene product serves as the
cellular receptor of VV, a plasmid expressing the full-length A1
cDNA in mammalian cells was prepared and used to determine the
role of A1 cDNA clone in virus entry. Futur study will determine
ifoveroxperssion of the A1 gene product will result in increase
of virus binding.This study also intend to investigate the role
of viral envelope proteins in virus attachment during virus
entry. Each envelope proteins were overexpressed in E. coli and
their ability to interfere with mAb B2 interactionwith cells was
measured. On the other hand, mutant viruses defective of A34R,
A36R, B5R, or F13L of envelope proteins were also used to
determine the effect of envelope proteins in virus entry.
Results from these expermentsrevealed that lack of above
envelope protein does not affect the mechanism ofvirus entry.
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